The invention relates to a false twist texturing machine for texturing a plurality of thermoplastic multifilament yarns.
A false twist texturing machine of this general type is disclosed, for example, in U.S. Pat. No. 5,644,908. The false twist texturing machine as described in that patent comprises a plurality of processing stations, each of which produces a crimped yarn from a fed flat yarn. To this end, a first feed system withdraws the yarn from a feed yarn package and advances it into a false twist zone. The false twist zone includes a heating device, a cooling device, and a false twist unit mounted in series. Within the false twist zone, the yarn undergoes a drawing and setting. The false twist unit produces a twist, which extends opposite to the direction of the advancing yarn, so that within the cooling device and the heating device, in which the yarn undergoes thermal treatment, the yarn exhibits a false twist, which is removed at the outlet of the false twist unit.
For a thermal aftertreatment, a second feed system advances the yarn through a second heater as well as to a takeup device, which winds the yarn to a package. Since after removing the false twist, a greater or lesser residual twist remains in the yarn as a function of the process, the known texturing machine includes a countertwist device in the form of an entanglement nozzle upstream of the takeup device. The countertwist device leads to a twist treatment, which removes the residual twist in the yarn.
Whether or not, and the extent a twist treatment by the countertwist device is needed, depends both on the polymer type of the yarn and on the adjusted process parameters, for example, the yarn speed.
Furthermore, for increasing the effectiveness of the twist treatment, it is known from WO99/09239 and corresponding U.S. Pat. No. 6,301,870 to arrange the countertwist device directly in the outlet region of the second heating device, so as to enable a well defined setting of the yarn in the heating device and, with that, a destruction of the residual twist. However, in so doing, one should consider that such heating devices, as disclosed, for example, in EP 0 595 086 B1 and corresponding U.S. Pat. No. 5,431,002, often cooperate with a guide tube for a thermal adjustment or for threading the yarn. Thus, for threading the yarn, the guide tube is connected to an injector, so that the yarn is taken in by suction at the inlet of the heating device, and so that it is advanced via the guide tube to a predetermined position within the machine.
It is therefore an object of the invention to provide the initially described false twist texturing machine with a countertwist device, which is easy to use when a twist treatment is needed, and which does not interfere with a pneumatic threading of the yarn at the beginning of a process.